1. Field of the Invention
The present invention relates generally to a method and apparatus for controlling a starter which is used for starting operation of an engine such as, for example, an internal combustion engine for a motor vehicle, an automobile or the like. In more particular, the present invention is concerned with a method and apparatus for protecting or preventing the starter (hereinafter also referred to as the engine starter) from overrunning upon starting of the engine operation.
2. Description of Related Art
In general, upon starting operation of the engine which may be an internal combustion engine or other, the engine starter is manually controlled through manipulation of a key switch by a user or driver, and the starter is electrically deenergized, i.e., stopped, after confirmation of engine noise generated upon starting of operation of the engine.
However, in the case of motor vehicles such as buses and others in which a driver""s seat is so distanced from the position at which the engine is installed that the engine starting noise is hard to hear or for other reasons such as acoustically low level of engine operation noise, noise generated after the engine operation has been started is difficult to recognize for the user. Consequently, there may unwantedly occur such situation in which the starter operation is continued over an extended time period notwithstanding of the fact that the engine operation has already been started, as a result of which an excessively large load is imposed on the starter.
Such being the circumstances, there have been proposed a variety of engine starting apparatuses and methods for automatically deenergizing or stopping the starter upon starting of engine operation with a view to protecting the starter from application of excessively large load, as is disclosed in a Japanese Patent Application Laid-Open Publication No. 145599/2000 (JP-A-12-145599) and others.
In the hitherto known or conventional apparatuses for preventing overrun of the starter as mentioned above, such arrangement is generally adopted that a starter power supply voltage (hereinafter also referred to simply as the starter supply voltage) is detected for automatically deenergizing or turning off the starter when the starter supply voltage has reached a predetermined reference voltage or alternatively the starter supply voltage exhibits a tendency of increasing continuously over a predetermined time period or duration.
In this conjunction, it is however noted that since the starter supply voltage is susceptible to variation in dependence on changes of the ambient temperature and the state of the power supply source, sufficient reliability can not be ensured for the detection of the starter supply voltage. As a result of this, such unwanted situation may arise that the starter is automatically turned off notwithstanding that the engine operation has not been started yet or the starter operation is continued regardless of the engine operation being started, giving rise to a problem.
Further, in another conventional apparatus, such arrangement is adopted that increasing of the engine rotation number (indicating starting of the engine operation) is detected on the basis of a relevant input signal supplied to an electronic control unit (ECU for short) or a voltage generated by an alternator to thereby turn off automatically the starter. In that case, however, extra expensiveness is involved for implementing the relevant circuit and interconnection for the starter, to disadvantage.
As is apparent from the foregoing, the conventional engine starter overrun preventing apparatuses and methods suffer problems. By way of example, in the case of the supply voltage detection apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 145599/2000, reliability for detecting the starter supply voltage is low, as a result of which there undesirably arise the problems that the starter is possibly turned off before the engine operation is started or the starter operation is continued even after the engine operation has been started, incurring overrun (application of excess load) of the starter.
Further, in the apparatus for detecting the engine rotation number on the basis of the signal inputted to the ECU or the voltage generated by the alternator, additional circuit and interconnection with the starter is required, incurring extra expensiveness.
In the light of the state of the art described above, it is an object of the present invention to solve the problems of the conventional techniques described above and provide a method and an apparatus for preventing overrun of an engine starter with enhanced reliability by detecting accurately the state in which the engine operation has been started on the basis of the starter supply voltage to thereby protect the engine starter from excessive load and burnout due to the overrun even if the engine and the starter should fall into a locked state, while sparing extra interconnection or wiring for the starter.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a first aspect of the present invention an apparatus for preventing overrun of an engine starter, which apparatus includes a voltage detecting means for measuring a supply voltage of the engine starter, a precedent starter voltage behavior storage means for storing a precedent voltage behavior of the supply voltage as a precedent starter voltage behavior, a current starter voltage behavior storage means for measuring a current voltage behavior of the supply voltage to thereby store the current voltage behavior as a current starter voltage behavior, an arithmetic means for reading out the current starter voltage behavior and the precedent starter voltage behavior to thereby arithmetically determine a voltage difference on the basis of difference between the current starter voltage behavior and the precedent starter voltage behavior, a comparison means for comparing the voltage difference with a predetermined voltage value, and a starter turn-off means for electrically deenergizing the engine starter upon detection on the basis of result of the comparison that a state in which the voltage difference remains short of the predetermined voltage value has continued for or longer than a predetermined time duration.
By virtue of the arrangement of the engine starter overrun preventing apparatus described above, the engine starter can be protected against overrun with enhanced reliability even in the case where the engine and the starter should fall into locked state, without need for additional expense for wiring/interconnection with the starter.
In a preferred mode for carrying out the invention, such arrangement may be adopted that the voltage waveform representing the precedent starter voltage behavior exhibits a phase difference less than one period relative to the voltage waveform representing the current starter voltage behavior.
With the arrangement described above, the state in which the engine operation has been started can distinctively be detected or recognized with high accuracy.
In another preferred mode for carrying out the invention, the arithmetic means may be so designed as to arithmetically determine a plurality of voltage differences on the basis of differences between the current starter voltage behavior and a plurality of the precedent starter voltage behaviors, respectively, which differ from one another in respect to the phase difference relative to the current starter voltage behavior. Further, the comparison means may be so designed as to compare the plurality of voltage differences, respectively, with the predetermined voltage value, while the starter turn-off means may be so designed as to electrically deenergize the engine starter when a state in which all of the above-mentioned voltage differences are short of the predetermined voltage value has continued for or longer than a predetermined time duration.
Owing to the arrangement described above, the state in which the engine operation has been started can distinctively be determined with high accuracy even if the period of the supply voltage should vary.
In yet another preferred mode for carrying out the invention, the precedent starter voltage behavior storage means may be comprised of a first precedent starter voltage behavior storage means for storing a first precedent starter voltage behavior which exhibits a first phase difference relative to the current starter voltage behavior, and a second precedent starter voltage behavior storage means for storing a second precedent starter voltage behavior which exhibits a second phase difference smaller than the first phase difference relative to the current starter voltage behavior, wherein the first precedent starter voltage behavior storage means may be designed to store the first precedent starter voltage behavior at a first sampling frequency, and the second precedent starter voltage behavior storage means may be designed to store the second precedent starter voltage behavior at a second sampling frequency which is higher than the first sampling frequency.
Owing to the arrangement described above, memory capacity for storing the starter voltage behaviors can be decreased.
Further, there is proposed according to a second aspect of the present invention, a method of preventing overrun of an engine starter by measuring a supply voltage for the engine starter to thereby electrically deenergize the engine starter when variation of the supply voltage makes disappearance. The above-mentioned method includes a first step of storing a precedent voltage behavior of the supply voltage as a precedent starter voltage behavior while measuring a current voltage behavior of the supply voltage to thereby store the current voltage behavior as a current starter voltage behavior, a second step of reading out the current starter voltage behavior and the precedent starter voltage behavior to thereby compare the current starter voltage behavior with the precedent starter voltage behavior, and a third step of electrically deenergizing the engine starter when a state in which a voltage difference arithmetically determined on the basis of difference between the current starter voltage behavior and the precedent starter voltage behavior remains short of a predetermined voltage value has continued for or longer than a predetermined time duration.
By virtue of the engine starter overrun preventing method described above, the engine starter can be protected against overrun with enhanced reliability even in the case where the engine and the starter should fall into locked state, without need for additional expense for wiring/interconnection with the starter.
In a mode for carrying out the second step of the method mentioned above, the current starter voltage behavior should preferably be compared with the precedent starter voltage behavior as read out which exhibits a phase difference less than one period relative to the current starter voltage behavior.
With the engine starter overrun preventing method described above, the state in which the engine operation has been started can distinctively be detected or recognized with high accuracy.
In another mode for carrying out the second step of the method mentioned above, the current starter voltage behavior should preferably be compared with a plurality of precedent starter voltage behaviors, respectively, which exhibit different phase differences, respectively, relative to the current starter voltage behavior.
Owing to the engine starter overrun preventing method described above, the state in which the engine operation has been started can distinctively be determined with high accuracy even if the period of the supply voltage should vary.
In yet another mode for carrying out the first step of the method mentioned above, the plurality of precedent voltage behaviors should preferably be sampled for storage with a plurality of sampling frequencies, respectively, which differ from each other.
Owing to the engine starter overrun preventing method described above, memory capacity for storing the starter voltage behaviors can be decreased.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.